+1 on Sunshield on Van Nuys Blvd in Sherman Oaks.
I had Xpel Prime XR Plus 55% tint installed at Sunshield about 1 1/2 years ago. Excellent work and they routinely do a ton of Teslas every week. Watching the technician install the tint on the rear window in one piece was like watching a master at work.
As for the amount of tint, that is completely personal taste. You do want to be aware of state laws about what tints are legal, etc. I personally chose a lighter tint because I did not want to darken the lightness and brightness of the white interior. With a ceramic tint, you still get lots of heat and UV rejection even with the lighter tints.
Before choosing your preferred tint, I suggest searching Youtube for videos on pros and cons of darker tints. Darker tints offer more privacy but they may impede nighttime viewing in low light conditions. During the day, you may also have an issue with the reflection of the white stripe across the dash interfering with your viewing of the side mirrors. These are additional reasons why I chose a lighter tint.